1. Field of the Invention
The present invention relates to a multicylinder internal combustion engine having an intake system including an intake manifold, and a resonator forming a resonance chamber communicating with an intake passage defined by the intake manifold.
2. Description of the Related Art
A known multicylinder internal combustion engine disclosed in, for example, JP 11-82203 A has an engine body provided with plural cylinders, an intake manifold having a header body defining an intake chamber, and runners defining branch passages branched off from the intake chamber, and a resonator defining a resonance chamber communicating with the intake chamber and formed integrally with the header body.
A multicylinder internal combustion engine is known as disclosed in, for example, JP 2002-339849 A. This known internal combustion engine is provided with an intake manifold having runners having reversed bends.
An internal combustion engine provided with an intake manifold having runners extending from joints on an engine body in a longitudinal direction perpendicular to a plane containing the axes of cylinders (reference plane) and parallel to a lateral direction in which cylinders are arranged is disadvantageous because of a large dimension of the engine with respect to the longitudinal direction. The above disadvantage can be eliminated by forming reversing bends in the runners such that the runners are closer to the engine body to reduce the dimension of the internal combustion engine with respect to the longitudinal direction. In this case, if a resonator is disposed on the inner side of the bends, the bends need to be shifted away from the engine body by a distance corresponding to the longitudinal dimension of the resonator and, consequently, the longitudinal dimension of the internal combustion engine cannot be fully reduced. In some cases, engine components including fuel pipes and fuel injection valves are disposed on the side of the engine body with respect to the intake manifold, i.e., on the inner side of the bends. In such a case, the size of the resonator is subject to restrictions to avoid interference between the engine components and the resonator and it is difficult to form the resonator in a necessary volume.
The present invention has been made under such circumstances and it is therefore an object of the present invention to provide a multicylinder internal combustion engine provided with an intake manifold and a resonator, and achieving both reducing its longitudinal dimension and forming the resonator in a necessary volume. Another object of the present invention is to facilitate forming a resonance chamber in a necessary volume without being subject to restrictions placed by engine components disposed on the side of an engine body with respect to a manifold, and by the engine body, and to form runners in high rigidity. A further object of the present invention is to facilitate forming a connecting passage connecting the body of an intake manifold and the resonance chamber of a resonator, and setting a resonance frequency, and to form the connecting passage in a small size.